Method for treating fluids

ABSTRACT

A fluid treating method for treating fluid to reduce the concentration of undesirable metal constituents contained therein is disclosed. The method utilizes a bed of metal particulate matter. The metal particulate matter comprises copper. Preferably, the metal particulate also contains zinc and can be in the form of an alloy. The fluid treated is often water, preferably, drinking water. Among the metals that may be effected by the present method are aluminum, arsenic, barium, cadmium, chromium, copper, gold, iron, lead, mercury, selenium and silver.

BACKGROUND AND DESCRIPTION OF THE INVENTION

This application is a continuation of application Ser. No. 239,339,filed May 6, 1994, now U.S. Pat. No. 5,433,856, which application is acontinuation of application Ser. No. 098,463, filed Jul. 28, 1993, nowU.S. Pat. No. 5,314,623, which application is a division of applicationSer. No. 980,316, filed Nov. 19, 1992, now U.S. Pat. No. 5,275,737,which application is a continuation of application Ser. No. 528,682,filed May 24, 1990, now abandoned, which application is acontinuation-in-part of application Ser. No. 352,719, filed May 12,1989, now abandoned, which application is a continuation of applicationSer. No. 205,628, filed May 31, 1988, now abandoned, which applicationis a continuation of application Ser. No. 070,591, filed Jul. 8, 1987,now abandoned, which application is a continuation of application Ser.No. 779,226, filed Sep. 23, 1985, now abandoned, which application is acontinuation of application Ser. No. 605,652, filed Apr. 30, 1984, nowabandoned.

The present invention generally relates to fluid treating and, moreparticularly, to apparatus and methods which are especially adapted forproviding for improved treatment of fluids. Industrial and domesticwater supplies often contain undesirable constituents which requiretreating prior to end use. Although capable of a variety of uses, thisinvention finds advantageous utility in the treatment of water to removeor inhibit the growth of undesirable constituents contained therein suchas, for example, dissolved chlorine and bacteria constituents.

In this regard, industrial and utility processes often require largeamounts of water for cooling. Many water cooling operations utilize heatexchange for primary heat regulation, with a resulting rise in thetemperature of the cooling water passing through the equipment. Thisrise in temperature promotes the growth of organisms already in thewater which in turn can result in fouling of the equipment such as byclogging of the system or by build-up of a biological slime layer on theheat exchange surfaces which greatly reduce their effectiveness.

Chlorination is the most common means of controlling bacteria in coolingwater systems as well as in drinking water systems. While the biocialproperties of hypochlorous acid are effective to kill bacteria thehypochlorous acid itself may be deliterious to other equipment ortreatment systems being used. In addition excess chlorine in drinkingwater often imparts an undesirable taste and odor to the water and theeffluent water can be harmful to the environment. In this regard, theEPA has established effluent limitations for residual chlorine and it isoften necessary to utilize dechlorination procedures to remove excessresidual chlorine resulting from over chlorination in order to complywith EPA guidelines.

Another advantageous utility of the present invention is in reducing theconcentration of undersirable metals present in the water. This is ofparticular value in the treatment of drinking water. Specific standardshave been set for many metals such that each metal must be below aspecific concentration. It is highly desirable to have available asimple treatment that will reduce the concentration of many undersirablemetals so that they will be within the established standards.

Similarly for other uses, the concentration of various metals need be atlow levels to prevent interference with the proposed use of the fluid.Various commercial and industrial uses can be adversely affected by thepresence of metallic contaminants such as aluminum, arsenic, barium,cadmium, chromium, copper, iron, lead, mercury, selenium and zinc. Thepresence of these and other undesirable metals in excess amounts caninterfere with the use of the fluids in various industrial applicationssuch as heat exchange fluids, lubricants, pressurization, and otherapplications.

Consequently, the presence of a method for substantially reducing theconcentration of undesirable metals in water, particularly drinkingwater, and other fluids is of the utmost importance.

In the field of fluid treating, and particularly in the field oftreating water for commercial, industrial and domestic use, a number ofsystems have been proposed, some or all of which have certainundesirable characteristics, drawbacks or disadvantages associatedtherewith.

For example, ion-exchange systems are commonly used to soften water andselectively remove specific impurities from the water. The active mediumof the ion-exchanger is an ion-exchange resin which is designed toremove undesirable constituents from the fluid and replace thoseundesirable constituents with a less undesirable constituent. Forinstance, a cation exchange resin employed to remove thehardness-producing elements of calcium and magnesium may be designed tosimultaneously give up sodium in exchange for the calcium and magnesiumcontained in the water which has passed through the ion-exchanger.Regardless of the specific ion-exchange resin used, eventually the bedof resin becomes exhausted and the unit must be removed from service andbe regenerated to become useful again. In addition to chemicalexhaustion iron bacteria can quickly fill an ion-exchange resin tank andplug chemical feed nozzles and other orifices. The resin is alsosusceptible to chemical degradation such as by excess chlorine presentfrom a bacteria treatment process. Accordingly, the ion-exchanger unitmust be carefully maintained and monitored to assure continuedacceptable performance.

Another popular type of process for treating water is reverse osmosiswherein pressure in excess of the osmotic pressure of the fluid is usedto force untreated water, normally at ambient temperature, through aselective membrane in a direction opposite to that normally observed inosmotic processes. The selective membrane is designed to allow the waterto permeate through while rejecting the dissolved undesirableconstituents. The success of this process depends in large part upon thedevelopment of suitable membranes. Membranes utilized in reverse osmosistypically experience a variety of temperature, chemical and pressurestability problems as well as speed and capacity limitations. Just asbacteria can foul heat exchangers so can it produce a fouling film onreverse osmosis membranes. If the water supply is treated with chlorineas an antibacterial agent the dissolved chlorine, although highlyeffective in combating bacteria, often has a deleterious effect onreverse osmosis membranes. Additionally, reverse osmotic equipment alsomust be carefully set up, maintained, and monitored. Accordingly,regardless of the sophistication of the technology used, if the end userfails to maintain the system and perform the necessary sampling requiredto ensure that the system is functioning to design specifications abreakdown in treatment can occur.

Still another popular water treatment process is the application ofactivated carbon, which is widely used for taste and odor control aswell as removal of organic contaminants from water by adsorbtion sinceactivated carbon is characterized by a high adsorbtivity for gases,vapors, and colloidal solids. However, similiar to the resin inion-exchangers, the adsorbtive capacity of the carbon is eventuallydepleted and the carbon either must be regenerated or replaced.Therefore a system incorporating activated carbon also requires carefulmonitoring to determine the effectiveness of the medium. An additionaldisadvantage of activated carbon is that it collects microorganismsincluding harmful bacteria and provides a medium upon which such harmfulbacteria can multiply. As a result, the activated carbon which issuppose to be purifying the water can end up contaminating the waterwith harmful bacteria. In an effort to overcome this disadvantage,manufacturers have attempted to provide a bacteriostatic activatedcarbon media by impregnating activated carbon with silver. However, suchefforts have not been totally satisfactory since it is difficult toachieve effective bacteriostatic concentrations of silver and keepwithin the EPA established guidelines for dissolved silver content.Silver also has other disadvantages associated with its use such as thecost of the silver itself can be prohibitive to economical watertreatment.

The present invention overcomes the undesirable characteristics,drawbacks and disadvantages of the prior art by providing a fluidtreating apparatus and method which employ metal particulate matter:having a redox potential which relative to the redox potential of theundesirable constituents sought to be treated favors spontaneousoxidation-reduction reactions between the metal and the undesirableconstituents and/or having bacteriostatic or bactericidal properties inthe case where the undesirable constituent sought to be treated is abacteria. The metal particulate matter can be of varying mesh size,preferably of from 4 to 400 mesh based on U.S. Standard screen sizes, ofany desired shape and is typically arranged in a loose bed confinedwithin a treating tank by means which prevent the escape of theparticulate matter but which, at the same time, permit fluid flowtherethrough. Alternatively, techniques for adhering the particles intoan aggregate porous body with the surface areas freely exposed can beutilized. Suitable techniques for forming such aggregate porous bodiesinclude sintering and processes wherein a binder is utilized whichresults in all, or substantially all, of the surface area of theparticles freely exposed for contacting fluids to be treated therewith.An important embodiment of the present invention is directed to anapparatus for treating water and a water treating method which employsmetal particulate matter such as zinc and copper, as well as mixturesand alloys thereof, to provide removal of undesirable contaminants suchas chlorine and bacteria. In this regard, an important aspect of thepresent invention involves a discovery that such a method will provideeconomical and long lasting removal of such undesirable contaminants andthereby greatly eliminate the weak link in most treatment systems i.e.maintaining and monitoring the system on a relatively frequent basis.

Another feature of the present invention involves a method of using sucha bed of metal particulate matter in conjuntion with another type offluid treating apparatus such as activated carbon, reverse osmosis, orion-exchange processes. In this regard, an important aspect of thepresent invention involves the removal of undesireable elements andcompounds such as chlorine and bacteria which may be detrimental to theoperation and life of other treatment methods such as activated carbon,reverse osmosis and ion-exchange processes.

Another feature of the present invention involves provision of anapparatus and a method of using such a bed of metal particulate matterin conjunction with another type of fluid treating apparatus such asactivated carbon, ion-exchange or reverse osmosis. In this regard, animportant aspect of the present invention involves the retardation ofthe growth of bacteria on such a medium and/or the destruction ofbacteria which may be present on such medium.

Another feature of the present invention involves adjusting the pH ofthe fluid and subsequently passing it through such a bed of metalparticulate matter. In this regard, an important aspect of the presentinvention involves regulating the pH of the fluid prior to treatment toenhance the removal of contaminants having pH dependentoxidation-reduction activities.

Another feature of the present invention involves the conjoint use ofdual containers having beds of such metal particulate matter arranged inseries with a pH feeder interposed therebetween. Such a method of fluidtreatment allows the user to take advantage of the pH of the sourcefluid at the inlet of the first container to treat the contaminants thatare more responsive to treatment at the original source fluid pH andthen to adjust the pH to treat contaminants which may be moreeffectively treated at another pH value to subsequently treat the fluidagain in the second container.

It is therefore, an important object to the present invention to providean improved fluid treating apparatus and method.

Another object of the invention is to provide a fluid treating apparatusand method which is economical to use, which has a relatively long lifeso as to avoid frequent maintenance and monitoring, and which eliminatesthe need to regenerate the treating medium and, accordingly, the need todispose of concentrated contaminants inherent in other conventionaltreatment processes such as reverse osmosis and ion-exchange processes.

Another object of the invention is to provide a novel method of treatingundesirable constituents such as chlorine and bacteria present in afluid such as water without concentrating such constitutents in thetreating medium.

Another object of the invention is to provide a fluid treating methodwhich includes treating the fluid by passing the raw fluid containingundesirable constituents through a bed of metallic particulate mattercharacterized by a redox potential which relative to the redox potentialof the undesirable constituents sought to be treated establishesconditions for spontaneous oxidation and reduction reactions between themetal particulate matter and the undesirable constituents when the fluidis in contact with the metal particles.

Another object of the present invention is to provide an improved methodof treating fluids wherein the fluids are first passed through a bed ofmetallic particulate matter to treat undesirable constituents presentsuch as chlorine which may be harmful to a conventional fluid treatmentprocess such as a reverse osmosis process or an ion-exchange process andto then pass the fluid through such a conventional treatment process.

Another object of the present invention is to provide an apparatus forand improved method of treating fluids wherein the fluids are firstpassed through a conventional fluid treating process such as anactivated carbon process and then the fluid is passed through a bed ofmetal particulate matter to treat undersirable constituents such asharmful bacteria.

Another object of the present invention is to provide an apparatus forand improved method of treating fluid wherein the fluids are passedthrough a bed containing both metal particulate matter as well as aconventional treating media such as activated carbon, ion-exchangeresins, or reverse osmosis membranes to treat undesirable constituents.

Another object of the present invention is to provide an improved methodfor treating fluids so as to reduce the concentration of undersirablemetals to levels which the fluids can be used in a variety of industrialapplications by means of a system which does not-require continuedreplenishment of the fluid treating system.

Another object of the present invention is to provide an improved methodfor treating water to reduce the concentration of undesirable metals tolevels wherein the water meets standards for the concentration of suchmetallic contaminants set for drinking water.

These objects and other objects and advantages of the invention areaccomplished by providing fluid treating apparatus which includes a bedof metal particulate matter and a method for treating fluid whichincludes passing fluid containing undesirable elements and compoundsthrough such a bed of metal particulate matter. The particulate matteris preferably chosen from metals such as zinc and copper as well asmixtures and alloys thereof, having favorable redox potentials relativeto the undesirable constituents such as chlorine sought to be treated soas to establish conditions for spontaneous oxidation and reductionreactions between the metal particulate matter and the undesirableconstituents when the fluid is in contact with the metal particlesand/or having bacteriostatic or bactericidal properties in the casewhere an undesirable constituent sought to be treated is a bacteria.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a vertical sectional view of one form of fluid treatingapparatus of the invention, showing a loose bed of metal particulatematter; fluid treating apparatus of the invention, showing a bed ofactivated carbon and a bed of metal particulate matter separate fromeach other but contained in a common housing;

FIG. 2 is a vertical sectional view of one form of fluid treatingapparatus of the invention for spontaneous oxidation and reductionreactions between the metal particulate matter and the undesirableconstituents when the fluid is in contact with the metal particlesand/or having bacteriostatic or bactericidal properties in the casewhere an undesirable constituent sought to be treated is a bacteria;

FIG. 3 is a vertical sectional view of one form of fluid treatingapparatus of the invention, showing a bed of activated carbon and a bedof metal .particulate matter in series; and

FIG. 4 is a vertical sectional view of one form of fluid treatingapparatus of the invention, shying a conventional treatment process suchas a bed of activated carbon, and a bed of metal particulate mattercontained in a common housing.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Although an important aspect of the present invention is directed to thetreatment of water, especially drinking water, it will be appreciatedthat the apparatus and method of this invention may also findadvantageous utility in the treatment of a variety of other sourcefluids with various different undesirable contaminants. For purposes ofillustration only therefore, this invention will, in most part, bedescribed by reference to an embodiment wherein water is the sourcefluid being treated.

It has now been discovered that the composition of a given water supplycan be altered with respect to certain contaminants therein such asdissolved chlorine and nitrates by bringing the water in contact withmetals such as aluminum, steel, zinc, tin, and copper as well asmixtures and alloys thereof. For example, it has been noted that whenwater containing high concentrations of dissolved chlorine is passedthrough a canister housing metallic particulate matter such as brassthat the detectable chlorine level of the effluent water is greatlyreduced, if not totally eliminated.

In addition, the concentration of undersirable metals can be reducedwhen water is passed through a canister housing metallic particulatematerial comprising copper and zinc, such as brass. Thus, theconcentration of metals such as aluminum, arsenic, barium, cadmium,chromium, copper, gold, iron, lead, mercury, selenium and silver can bereduced when a fluid, such as water, containing such metals, is treatedby passing it through a bed of metal particles, comprising copper andzinc, which can be in the form of a brass alloy.

An explanation for this reduction in the concentration of undersirablemetals by passing the water or other fluids containing these metalsthrough a bed of metallic particulate material comprising copper andzinc is that there is an electrical field formed of the copper and zinc.In this electrical field, the metals in the fluid become ions which canbe replaced by the copper or zinc ions which go into solution. Thereplaced metallic ion plates out on the brass or other form of copperand zinc metallic particulate. It has been noted that the materialplated out is dendritic and porous. Consequently, this plating out doesnot prevent the metallic particulate material from continuing tofunction but it does decrease the rate of replacement of undesirablemetal from the fluid possibly because turbulence is reduced and thereplacement of the undesired metal ion becomes diffusive.

It has also been discovered that such a method of fluid treatment isalso effective under certain operating conditions to significantlyreduce and/or eliminate the nitrate concentration of the effluent water.Additionally, it has been discovered that fluid treating mediacontaining brass particulate matter acts as an effective bacteriocidaland/or bacteriostatic agent with respect to common bacterialcontaminants such as E. coli and Pseudomonas. It has also beendiscovered that when water containing dissolved iron, such as ferrousiron, which could stain clothing upon contact therewith is passedthrough a bed of brass that the effluent water is apparently free ofdissolved iron and does not stain clothing upon contact therewith. Ithas further been discovered that when water contaminated with tannins ispassed through a bed of brass that the effluent water is clear andapparently tannin free. As a result of such findings, it is presumedthat the present development may have widespread application to othertypes of inorganic contaminants such as hydrogen sulphide and sulphurdioxide to name but a few as well as organic contaminants.

Moreover, it is believed that the useful life of such a method of fluidtreatment under normal operating conditions, would far exceed the usefullife of other conventional treating systems. Accordingly, such a findingrepresents a considerable step forward in the art in that it helps toeliminate one of the major drawbacks of conventional systems, i.e. theneed to frequently replenish the active source of treatment and theconcomitant need to constantly maintain and monitor the system.

In addition, such a method has wide spread potential application for avariety of domestic, commercial and industrial uses. For example notingthat chlorine and iodine are effective anti-bacterial agents, drinkingwater, especially in a foreign locale, could be treated by initiallychlorinating or iodizing the water and then the treated water could betransformed to a more palatable and safe form by contacting thechlorinated or iodized water with metal particles in accordance with thepresent invention.

As previously noted, this development is intended to have application toother fluid media besides water treatment including other liquid fluidmedia as well as gaseous fluid media by itself as well as gaseous fluidmedia dissolved in liquids. For example, removal of hazardous gassesespecially the halogens such as chlorine, bromine, and flourine bypassing those gasses through a canister housing a bed of metallic matteris contemplated by, and within the scope of, the present invention. Suchan application may provide an alternate method of purifying contaminatedair such as in a gas mask or may further be used as an alternative to orin conjunction with conventional scrubbing processes.

Referring now to the drawings, FIG. 1 shows the invention to betypically embodied in an apparatus generally designated 10 for treatinga fluid such as water, and shows that the apparatus includes an inlet12, an outlet 14, and a treating tank 16 containing a bed of metalparticulate matter 18. The treating tank 16 can be of a variety ofshapes and sizes depending upon the desired application. For example,treating tank 16 can take the form of a cannister as depicted in FIG. 1.

As shown in FIG. 1 fluid treating tank 16 comprises impermeable sidewalls 20, and top and bottom walls 22 and 24. Top wall 22 and bottomwall 24 include inlet 12 and outlet 14 permitting flow of fluid to betreated respectively into and out of the treating tank 16. The fluidtreating tank 16 further comprises, foraminous or permeable top andbottom plates 26 and 28 which allow fluid to pass respectively into andout of the fluid treating tank 16 while preventing the escape of themetal particulate matter 18. In accordance with a further aspect of thepresent invention, the bed of metal particulate matter may be used incombination or conjunction with other fluid treating mediums to providean enhanced fluid treating system.

FIGS. 2-4 illustrate examples of such enhanced fluid treating systems.In FIG. 2 apparatus 40 includes fluid treating tank 16 which furthercomprises a middle foraminous or permeable plate 42 dividing the tank 16into an upper chamber 44 and a lower chamber 46. The upper chamber 44includes a conventional fluid treating medium such as activated carbon48 and the lower chamber includes the bed of metal particulate matter18. In FIG. 4 apparatus 50 includes fluid treating tank 16 whichincludes a conventional fluid treating medium such as, for example,activated carbon 48 mingled with the metal particulate matter 18.Treating medium 48 could, of course, also be any conventional treatingmedia such as, for another example, a reverse osmosis media in whichcase fine mesh metal particulate matter 18 could be flocked onto themembrane.

In FIG. 3 apparatus 60 includes two fluid treating tanks 62 and 16 whichare connected in series. The fluid treating tank 62 includes an inlet 64and an outlet 66 which is connected to inlet 12 of fluid treating tank16. Fluid treating tank 62 includes a conventional treating medium suchas a bed of activated carbon 66. The fluid treating tank 62 comprisesimpermeable side walls 68, and top and bottom walls 70 and 72. Top wall70 and bottom wall 72 include inlet 64 and outlet 66 permitting flow offluid to be treated respectively into and out of the treating tank 62.The fluid treating tank 62 further comprises foraminous or permeable topand bottom plates 74 and 76 which allow fluid to pass respectively intoand out of treating tank 62 while preventing the escape of the activatedcarbon 66.

It will be appreciated that the relative positioning of the fluidtreating mediums depicted in FIGS. 2 and 3 and described above can beinverted depending upon the desired application. For example, aspreviously described, if the conventional treating medium is activatedcarbon it may be desirable to have the bed of metal particulate matterdownstream of the activated carbon to treat any harmful bacteriacontained in the fluid leaving the bed of activated carbon. On the otherhand if the conventional treating medium is a reverse osmosis orion-exchange media it may be desirable to have the bed of metalparticulate matter upstream of such medium to eliminate constituentssuch as dissolved chlorine which may be deleterious to such medium.

The present invention contemplates the use of several different metalsas well as mixtures and alloys thereof. It is hypothesized, withoutbeing limited to any particular theory of the invention, that thetreatment process of the present invention, at least with respect toinorganic constituents such as dissolved chlorine, is accomplished byspontaneous oxidation-reduction reactions. Accordingly it is believedthat the metal particulate matter should be selected from a group ofmetals including mixtures and alloys thereof, which are relatively goodredox agents relative to the undesirable constituents sought to betreated so as to establish conditions for spontaneous oxidation andreduction reactions between the metal particulate matter and theundesirable constituents when the fluid is in contact with the metalparticulate matter.

The relative tendencies of different species to be reduced or oxidizedcan be predicted from their standard reduction potentials (E° values at25° C.). By comparing the E° values for different species it is possibleto determine whether an oxidation-reduction will spontaneously occur. Inaccordance with the present invention, metals which are relatively goodredox agents relative to the elements or compounds sought to be treatedare those metals which are predicted to react spontaneously with suchelements and compounds.

For example, chlorine dissolved in water having a pH of approximately 7and at 25° C. exists as HOCl and ClO⁻ with HOCl predominating on theacid side and ClO⁻⁻ predominating on the base side. Assuming forsimplicity that ClO⁻⁻ is the reacting species the following redoxreactions are representative of those contemplated by the presentinvention: ##EQU1## As calculated, both zinc and copper should eachreact spontaneously with hypochlorite (ClO⁻⁻) with the zinctheoretically being more spontaneous since it has the more positivepotential.

Zinc and copper are preferred metals since both are relatively goodreducing agents with respect to common inorganic contaminants such aschlorine and since both can be tolerated in solution in moderateconcentrations without adverse effects. While other metals such as ironand aluminum are also theoretically good reducing agents such metalshave disadvantages, which limit their applicability to universalcommercial use. For example, while relatively high concentrations ofiron can be tolerated in drinking water without toxic effects, suchconcentrations tend to feed iron based bacteria and also tend to stainitems such as clothes when used domestically. In this regard, it has nowbeen discovered that when water containing dissolved iron, such asferrous iron which could stain clothing upon contact therewith, ispassed through a bed of brass that the effluent water is apparently freeof dissolved iron and does not stain clothing upon contact therewith.Additionally, an iron based bed of metal particulate is inclined topremature clogging. Similarly, aluminum based treatment beds tend toscab, i.e. an oxide film forms on the surface, thus becoming practicallyineffective after short use.

In practice it has been found that a zinc and copper alloy, such asbrass is more effective in the removal of dissolved chlorine andundesired metals than is either pure zinc or pure copper or aheterogeneous mixture thereof. In addition to the noted effectiveness ofbrass, brass is also a preferred metal from the viewpoint of chemicalsafety. This is especially true in aqueous media since brass does nothave the violent reactivity to aqueous fluids as do metals such as puresodium, potasium, calcium or zinc.

A copper/zinc alloy such as brass is also a preferred metal from theviewpoint of effluent dissolved metal concentrations. In this regard, itis noted that by-products of the redox reactions between zinc, copperand alloys thereof with inorganic contaminants such as dissolvedchlorine are dissolved zinc, dissolved copper, and mixtures thereof,respectively. When zinc or copper are used alone to treat excessivelychlorinated drinking water it is possible to effect dissolved metalconcentrations which, while relatively dilute, exceed EPA recommendedguidelines. While, as discussed further below, any resulting undesirablemetal concentration could be effectively removed by further treatmentwith conventional treatment processes such as ion-exchange or reverseosmosis processes, it has been found that when a copper/zinc alloy suchas brass is utilized as the treatment medium, the resulting dissolvedmetal concentrations fall well within current EPA guidelines fordissolved zinc and dissolved copper in drinking water.

As noted above, a further embodiment of the present invention is amethod for purification whereby the water is passed through both a bedof metallic particulate matter such as brass and a conventionaltreatment process such as reverse osmosis or ion-exchange or activatedcarbon. This could be especially advantageous due to the fact thatsemipermeable membranes such as cellulose acetate often used in reverseosmosis treatment methods are often susceptible to degredation bydissolved chlorine as is divinylbenzene which is often used to crosslink ion-exchange resins. Utilization of a bed of brass in conjunctionwith the reverse osmosis membrane or ion-exchanger could substantiallylengthen the life of the membrane or resin. Additionally, each of thereverse osmosis, ion-exchange and activated carbon conventionaltreatment methods are susceptible to bacterial fouling and/or bacterialbuild-up. In this regard, it has been found that the use of copper or acopper alloy such as brass in a treating system is effective to combatbacteria such as E. coli commonly found in sewage contaminated watersupplies as well as other undesirious organisms such as Pseudomonas.

It will be appreciated that the term "brass" is used herein to indicatea copper-zinc alloy, in general, and that such alloy can contain otherconstituents and/or be commonly denominated by different nomenclature.For example, alloys commonly termed bronze containing copper and zinc,such as, but not limited to, architectural bronze composed ofapproximately 57% Cu-40% Zn-3% Pb, manganese bronze A composed ofapproximately 58.5% Cu-39% Zn-1.4% Fe-1% Sn-0.1% Mn and manganese bronzeB composed of 65.5% Cu-23.3% Zn-4.5% Al-3.7% Mn-3% Fe as well as othermetals such as Muntz metal composed of 60% Cu-40% Zn are generallyreferred to as brasses herein and are within the scope of the presentinvention.

Where brass is the chosen metal, it has been found that washing thebrass such as with a hydrochloric acid solution and then rinsing thebrass will cleanse the surface of the brass of contaminants, such asiron filings or other foreign matter, which might interfere with theactivity of the brass. However, it has additionally been noted that thesurface of the brass which is exposed to the atmosphere or to a sourcefluid such as water may develop a greenish rust which may be a carbonateand/or oxide complex. When the surface itself is physically scraped toremove the greenish rust, the removed rust also shows excellentpurifiying tendencies.

Qualitive analysis of water to which chlorine was added and which wastreated by being passed through a bed of brass showed that such treatingconsistently effected a decrease in the amount of chlorine in the water.Set forth below are Examples I and II which describe quantitativeanaylsis conducted by independent laboratories of the composition of thebrass used to treat the water and of the water treated, respectively,both before and after treatment. Analysis of the brass, as described inExample I below, indicated that passing water through the bed of brassdid alter the composition of the brass as might be expected ifoxidation-reduction processes were occurring. As shown in Example IIbelow, the independent laboratory analysis of the influent and effluentwater passed through the bed of brass did confirm the virtualelimination of the chlorine contained in the influent water.

EXAMPLE I

Water was passed through a cylinder housing a 3 inch by 6 inch bed of14×30 mesh brass trapped between screens to prevent the escape of thebrass. The water passed through the brass bed originated from theVillage of Constantine, Mich. water supply which is not chlorinated butwhich contains dissolved nitrates from approximately 10 to 13 parts permillion. Amounts of chlorine, from approximately 2 to 13 parts permillion, were introduced into the influent water to test the extent ofdecrease in the chlorine level. After approximately 51,000 gallons ofwater had passed through the bed of brass it was observed that the bedhad diminished in height about one half inch. A fresh sample of brassfrom which the bed was composed was analyzed as was a sample of brasstaken from the bed after approximately 51,000 gallons of water hadpassed therethrough.

Elemental composition of these samples was determined by DirectlyCoupled Plasma-Atomic Emission Spectroscopy using a Beckman SpectraspanVI Spectrometer. Samples were prepared for plasma emission analysis bydissolving 0.1000 grams into 20 milliliters of a 50/50 concentratednitric acid/distilled water mixture. Total solution weight was thenbrought to 100.00 grams by the addition of distilled water.

Elemental composition was determined as the average of values obtainedfrom the following emission lines for each element: Copper; 213.598 nm.,233.008 nm.; Iron; 238.204 nm., 259.940 nm., 371.994 nm.; Zinc: 213.856nm., 206.200 nm., 202.548 nm.; Lead; 405.783 nm., 283.306 nm., 368.348nm. The results were:

    ______________________________________    BRASS ANALYSIS    BEFORE TREATMENT     AFTER TREATMENT    ______________________________________    % Copper            59.2             65.0    % Zinc  35.2             27.8    % Lead  2.5              2.5    % Iron  0.2              0.2    ______________________________________

Emission wavelengths for tin and aluminum were also examined, but theseelements could not be detected at the 1 to 1000 sample dilution.

EXAMPLE II

Two sets of samples of influent and effluent water which had passedthrough the brass bed of Example I after it had been used to treatapproximately 51,000 gallons of water were sent to an independentlaboratory for analysis. Sample Set A was unchlorinated tap watersupplied by the Village of Constantine, Mich. water supply and sampleSet B was tap water to which chlorine was added. The results of theanalysis follow:

    ______________________________________    PARAMETER    UNITS        IN     OUT    ______________________________________    SAMPLE SET A    Nitrite Nitrogen                 mg/l         10.35  9.34    Nitrate & Nitrite                 mg/l         .01    .01    Organic Nitrogen                 mg/l         10.35  9.35    Aluminum (Al)                 mg/l         0.5    0.5    Copper (Cu)  mg/l         0.04   0.27    Iron (Fe)    mg/l         0.05   0.34    Potassium (K)                 mg/l         1.00   1.47    Sodium (Na)  mg/l         3.8    5.2    Zinc (Zn)    mg/l         0.12   1.3    SAMPLE SET B    Chloride     mg/l         29.5   32.0    Chlorine     mg/l         13.0   0.1    Nitrate Nitrogen                 mg/l         11.35  10.69    Nitrite Nitrogen                 mg/l         .01    0.01    Nitrate & Nitrite                 mg/l         11.35  10.69    Aluminum (Al)                 mg/l         0.5    0.5    Calcium (Ca) mg/l         93.0   94    Copper (Cu)  mg/l         0.05   .26    Magnesium (Mg)                 mg/l         24.0   24.4    Potassium (K)                 mg/l         1.02   1.06    Sodium (Na)  mg/l         17.1   17.8    Zinc (Zn)    mg/l         0.11   4.5    ______________________________________

The preceding Examples are offered to illustrate the method of thepresent invention and the effect produced thereby and are not intendedto limit the general scope thereof. As shown best by the results ofSample Set B of Example II the method of the present invention iseffective to remove undesireable contaminants such as dissolvedchlorine. The concentration of cations such as zinc and copper cationsdid increase in the effluent as would be expected if anoxidation-reduction process were taking place.

Additionally, it has been observed that influent tap water having a pHof approximately 6.9 has a pH of approximately 7.2 after passing throughthe brass bed. Further, it has been noted that the pH value of water, ingeneral, and especially water having acidic pH values, is raised as aresult of having been passed through a brass treatment bed. This is anespecially advantageous feature of the present invention since chlorideions are commonly present in drinking water and since chloride is theresulting ion after treatment with brass when chlorine is the targetcontaminant. Chloride ions are potentially corrosive agents in an acidicmedia. The concommitant increase in pH value of the treated water as itis being treated tends to neutralize the potentially corrosive effect ofany existing chloride ions.

As shown by the results of both Sample Sets A and B of Example II thetreatment process also effected a decrease in the level of dissolvednitrates in the water. It has been found that transformation ofdissolved nitrates is enhanced and the concentration of the dissolvednitrates is significantly reduced by the present treatment process whenthe fluid medium is at least slightly acidic such as having a pH of 6.5or less. It has been found that the transformation of dissolved nitratesin an acidic medium is, to some extent, reversible, i.e. it is possibleby subsequently increasing the pH value of the effluent to detect thepresence of dissolved nitrates. In this regard, it has quiteunexpectedly been found that nitrate removal can also be effectively,and apparently nonreversibly, be effected at relatively high pH valuessuch as for example a pH value of 10-12.

Therefore if the undesirable constituent is more effectively removed inan acidic media a conventional acid feeder can be incorporated into thewater treatment method. Alternatively, if the undesirable constituent ismore effectively removed in a basic media a conventional base feederpretreatment can be used. Where multiple elements or compounds aretreated requiring different pH values the water to be treated may bepassed through successive beds of metal particulate matter, such asbrass, arranged in series with the appropriate conventional acid or basefeeders interposed therebetween.

It has further been found that the speed and degree of removal ofcontaminants is dependent upon the contact time of the fluid with themetal. Accordingly, increasing the contact surface area of the bed suchas by using a smaller metal mesh will enhance the speed and degree ofremoval. Alternatively, or in conjunction therewith, the fluid flow ratecould be decreased to allow a longer contact period. It has stillfurther been found that supplying oxygen to the fluid or metalparticulate matter such as by bubbling air through the fluid or exposingthe bed of metal particulate matter to the atmosphere can enhance thetreatment process.

It has been found that the mesh size of the metal particulate matter canvary appreciably and still be effective at treating the fluid. Forexample, typical mesh sizes of the metal particulate matter will rangefrom 4 to 400 mesh based on U.S. Standard screen sizes and although meshsizes both above and below this range can be utilized mesh sizes from 4to 30 mesh usually will be preferred for most applications. It will beappreciated that the metal particulate matter can be supplied in otheralternate forms such as in aggregate porous bodies made by adhering theparticulate matter into porous bodies of any desired shape. Suitabletechniques for forming such aggregate porous bodies include sinteringand processes wherein a binder is utilized which results in all, orsubstantially all, of the surface area of the particles freely exposedfor contacting fluids to be treated therewith.

It has been found that brasses composed of respective percentage, byweight, of copper and zinc, yield different effluent concentrations ofdissolved metals. In this regard, and with respect to current effluentlimitations, brasses containing approximately a 1:1 ratio of copper tozinc are preferred, brasses containing approximately a 3:2 ratio ofcopper to zinc are more preferred and brasses containing approximately a7:3 ratio of copper to zinc are most preferred. It will of course beappreciated that since copper is a better bacteriocidal andbacteriostatic agent than is zinc that increasing the percentage ofcopper in the brass should produce an enhancedbacteriocidal/bacteriostatic treating media.

In treating fluids, particularly water, to reduce the concentration ofundesirable metals therefrom, it has been found possible to use metalparticulate matter, comprising copper and zinc in a weight ratio ofcopper to zinc of between about 1:9 and about 9:1, preferably betweenabout 3:7 and about 9:1. It had been found that using the weight ratiosof copper to zinc of between about 4:6 and 6:4 in certain instances mayincrease the effective useful life of the brass alloy in reducing theconcentration of undesirable metal in the fluid, particularly water.

It is contemplated that a 20 inch bed of 14×30 mesh brass housed in acylinder having a 6 inch diameter could accomodate the full pressurewater flow rate of a domestic home user and effectively treat influentchlorinated water for many years without replacing the bed of brass.

Set forth below are Examples III and IV which describe quantitativeanalysis conducted by an independent laboratory of water innoculatedwith E. coli and Pseudomonas bacteria, respectively, before and aftertreatment with each of brass; a mixture of 50% brass and 50% activatedcarbon; zinc; copper; and, activated carbon.

EXAMPLE III

Initial innoculum Escherichia coli was prepared from an overnight stockculture grown on standard methods agar and suspended in phosphatebuffered saline. Single strength tryptic soy broth was added to theinnoculum suspension to achieve a final tryptic soy broth concentrationof 10% so to provide adequate available nutrient to allow bacterialgrowth.

Approximately 100 cubic centimeters of each of the following testmaterial were placed into respective 400 ml. beakers:

Test Materials

1. Brass shavings (approximate elemental composition, 70% Cu and 30% Znby weight);

2. 50:50 mixture of brass (as above) and commercial activated carbonparticles;

3. Particulate zinc;

4. Particulate copper;

5. Commercial activated carbon.

The innoculum (prepared as stated above) was added to each beakersufficient to bring the fluid level just below the surface of the testmaterial. A microbial count of the innoculum was made prior to additionof the test material. Each beaker was incubated at room temperature for16 hours, and a microbial count was then performed on 1 ml. of theavailable fluid.

The results* were:

    ______________________________________                Initial E. coli  Final E. coli    Test Material                Inoculum: CFU/ml Liquid                                 CFU/ml Liquid    ______________________________________    Brass       33,000,000           <10    50% Brass/50%                33,000,000         35,000    Activated Carbon    Zinc        33,000,000         810,000    Copper      33,000,000            10    Activated Carbon                   23,000        3,000,000    ______________________________________

The tests using brass, 50% brass/50% activated carbon, zinc and copperwere performed on the same day using the same innoculum. The test usingactivated carbon was performed by the same independent laboratory at alater date using a different inoculum prepared in the same manner asdescribed above.

EXAMPLE IV

Initial innoculum Pseudomonas was prepared from an overnight stockculture grown on standard methods agar and suspended in phosphatebuffered saline. Single strength tryptic soy broth was added to theinnoculum suspension to achieve a final tryptic soy broth concentrationof 10% so to provide adequate available nutrient to allow bacterialgrowth.

Approximately 100 cubic centimeters of each of the following testmaterial were placed into respective 400 ml. beakers:

Test Materials

1. Brass shavings (approximate elemental composition: 70% Cu and 30% Znby weight);

2. 50:50 mixture of brass (as above) and commercial activated carbonparticles;

3. Particulate zinc;

4. Particulate copper;

5. Commercial activated carbon.

The innoculum (prepared as stated above) was added to each beakersufficient to bring the fluid level just below the surface of the testmaterial. A microbial count of the innoculum was made prior to additionof the test material. Each beaker was incubated at room temperature for16 hours, and a microbial count was then performed on 1 ml. of theavailable fluid.

The results were:

    ______________________________________              Initial Pseudomonas                               Final Pseudomonas    Test Material              Inoculum: CFU/ml Liquid                               CFU/ml Liquid    ______________________________________    Brass     2,300,000          20,000    50% Brass/50%              2,300,000        1,300,000    Activated    Carbon    Zinc      2,300,000        1,000,000    Copper    2,300,000          15,000    Activated 2,300,000        2,000,000    Carbon    ______________________________________

The preceding Examples are offered to illustrate the method of thepresent invention and the effect produced thereby and are not intendedto limit the general scope thereof. As shown above copper and brass bothproved to be exceptionally effective bacteriocidal agents when usedalone as treating medias. As best illustrated by Example III, activatedcarbon provided a breeding ground for bacterial growth and over a 100fold increase in bacteria was experienced when activated carbon was usedalone. However, by mixing brass shavings with the activated carbon, aneffective bacteriostatic media was achieved. It will of course beappreciated that copper or brass can be used in conjunction with otherfluid treating processes such as ion-exchange and reverse osmosisprocesses to achieve similar bacteriocidal/bacteriostatic medias. Itwill further be appreciated that the metal bacteriocide can be discretefrom the other treating media or integrated therewith such as byimpregnating activated carbon with copper or brass. Example IVillustrates that the present invention is also effective to control thegrowth of organisms having a greater resistance to antimicrobial agentssuch as Pseudomonas.

Additional tests were performed to establish the effectiveness of thebrass in reducing the concentration of undesirable metals in fluids,especially water.

EXAMPLE V

Brass alloy filings (5 pounds) containing about 50 weight percent copperand about 50 weight percent zinc were placed on a 0.5 inch thick bed ofquartz wool in a polytetrafluoropolyethylene tube, having an insidediameter of 1.75 inches and a length of 20 inches. The water solutionwas fed upward through the bed of quartz wool.

The flow of water through the brass was at a rate slightly lower thanone gallon per minute. Flow of water was continued until any one of themetals in the water reached the maximum allowable effluent level. Thisoccurred after 238,000 gallons of water had flown through the brass. Atthis time, the water was analyzed for the content of other metals andcontaminants. The effluent water had no noticeable additional taste orodor.

    ______________________________________                  CONCENTRATIONS                  (mg/l)    CHEMICAL        INPUT    OUTPUT    ______________________________________    Trihalomethane  0.51     0.51    Lead            0.16     0.0009    Fluoride        8.20     6.88    Nitrate         30.2     19.9    Barium          10.0     0.000    Arsenic         0.33     0.001    Cadmium         0.030    0.003    Chromium (VI)   0.152    0.052    Chromium (III)  0.163    0.065    Selenium        0.105    0.000    Mercury         0.0063   0.000    Endrin          0.0008   0.0008    Lindane         0.013    0.013    Methoxychlor    0.30     0.30    Toxaphene       0.016    0.016    2,4-D           0.30     0.30    Silver          0.032    0.032    Copper          0.000    5.88    Zinc            0.000    8.99    Sulfur          0.50     0.000    Chlorine        2.0      1.34    ______________________________________

EXAMPLE VI

This test was performed using brass containing about 50 weight percentcopper and 50 weight percent zinc and also having granular activatedcarbon in a polyvinyl chloride cylinder having a nominal outsidediameter of 3.5 inches and polyvinyl caps. The cylinder had a length of12.5 inches. Water was passed through the cylinder at a rate of 1 gallonper minute. The input and output water were analyzed for chemicalcontent with results as follows:

    ______________________________________                  CONCENTRATIONS                  (mg/l)    CHEMICAL        INPUT    OUTPUT    ______________________________________    Trihalomethane  0.53     0.07    Lead            0.12     0.000    Fluoride        8.12     1.07    Nitrate         30.0     5.37    Barium          10.0     0.02    Arsenic         0.37     0.000    Cadmium         0.030    0.004    Chromium (XI)   0.150    0.03    Chromium (III)  0.151    0.008    Selenium        0.108    0.006    Mercury         0.006    0.000    Endrin          0.0008   0.0001    Lindane         0.014    0.003    Methoxychlor    0.33     0.07    Toxaphene       0.018    0.001    2,4-D           0.33     0.077    Silver          0.030    0.008    Copper          0.000    2.23    Zinc            0.000    2.39    ______________________________________

EXAMPLE VII

The unit used in this test was a fiber wound reinforced resin cylinder,7.87 inches in diameter and 35 inches in length. The bottom of thecylinder is connected to a cylindrical plastic section which acts as abase that keeps the unit erect. The unit contained brass having acomposition of about 50 weight percent copper and 50 weight percent zincand a granular activated carbon. The water flow rate was 6.1 gallons perminute. The test was continued until one of the metallic inorganicelemental components reached the maximum allowable effluentconcentration. This occurred with chromium after 393,500 gallons ofwater passed through the unit. The input water and the output water wereanalyzed for chemical content with results as follows:

    ______________________________________                  CONCENTRATIONS                  (mg/l)    CHEMICAL        INPUT    OUTPUT    ______________________________________    Trihalomethane  0.50     0.039    Lead            0.15     0.009    Fluoride        8.00     0.00    Nitrate         30.0     7.9    Barium          10.0     0.000    Arsenic         0.33     0.002    Cadmium         0.031    0.007    Chromium (VI)   0.152    0.044    Chromium (III)  0.153    0.045    Selenium        0.105    0.000    Mercury         0.0063   0.000    Endrin          0.0008   0.0008    Lindane         0.013    0.0035    Methoxychlor    0.30     0.032    Toxaphene       0.015    0.003    2,4-D           0.30     0.071    Silver          0.032    0.002    Sulfur          0.50     0.000    Chlorine        2.0      0.39    ______________________________________

EXAMPLE VIII

Chlorine (3 parts par million) and lead (2 parts per million) were addedto normal city water and passed through a unit containing brass (9.95cubic inches) comprised of copper (50 weight percent) and zinc (50weight percent) and granular activated carbon (73.94 cubic inches) at arate of 0.5 gallons per minute. After 10,000 gallons of the water waspassed through the brass, chemical analysis of ,the effluent watershowed that 99.1 weight percent of the chlorine and 99.4 weight percentof the lead had been removed from the water.

EXAMPLE IX

A test using brass alloy containing about 50 weight percent copper andabout 50 weight percent zinc and containing high grade carbon wasperformed with normal drinking water from Nottingham, England and withthis same drinking water spiked with certain metallic contaminants.

    ______________________________________                CONCENTRATION                (PARTS PER MILLION)    CHEMICAL      INFLUENT   EFFLUENT    ______________________________________    NORMAL DRINKING WATER    Copper        0.11275    0.02575    Lead          <0.01      <0.01    Cadmium       <0.01      <0.01    Arsenic       <0.01      <0.01    Iron          0.96       0.25    Aluminum      0.0275     0.0125    Chloride      32.5       31.5    Chlorine      0.635      0.05    SPIKED DRINKING WATER    Copper        5.00       0.018    Lead          5.00       <0.01    Cadmium       1.00       <0.01    Arsenic       0.24       <0.01    Iron          1.00       0.01    Aluminum      0.98       0.01    Chloride      237.00     162.00    Chlorine      5.00       <0.05    ______________________________________

EXAMPLE X

A test was performed with ordinary drinking water having a hardness of280 milligrams per liter and a pH of 6.98. The water was passed througha brass alloy containing about 50 weight percent copper and about 50weight percent zinc in a column having a depth of 250 millimeters and adiameter of 41 millimeters with the following results:

    ______________________________________            CONCENTRATION (mg/l)            AFTER            ONE PASS            THROUGH  AFTER    CHEMICAL  COLUMN     24 HRS.  48 HRS.                                         96 HRS.    ______________________________________    Copper    0.10       0.0      0.01   0.02    Zinc      0.57       0.1      0.17   0.42    Hardness  260        13       12.4   56    ______________________________________

EXAMPLE XI

A test performed passing normal drinking water having lead, copper,zinc, iron, aluminum and nitrate ions added thereto through a brassalloy comprising about 50 weight percent copper and about 50 weightpercent zinc for 18 hours at a rate of 600 mil. per minute.

    ______________________________________                  CONCENTRATIONS                  (mg/l)    CHEMICAL        INPUT    OUTPUT    ______________________________________    Lead            2.05     0.1    Iron            2.025    0.075    Copper          0.85     0.05    Aluminum        0.1      <0.005    Zinc            1.225    1.225    Nitrate         75       75    ______________________________________

EXAMPLE XII

A test was performed with normal drinking water to which chemicals wereadded. The water was passed through brass comprising about 50 weightpercent copper and about 50 weight percent zinc with the followingresults:

    ______________________________________                  CONCENTRATIONS                  (mg/l)    CHEMICAL        INFLUENT   EFFLUENT    ______________________________________    Aluminum        1.3        0.03    Arsenic         1.2        <0.05    Cadmium         1.3        0.02    Chlorine        3.0        <0.02    Iron            1.4        0.06    Lead            1.3        <0.05    Mercury         1.4        <0.05    Lindane         5.0        <0.1    Dieldrin        2.6        <0.1    Calcium Hardness                    138        98    Magnesium Hardness                    144        76    Total Hardness  182        174    Suspended Solids                    111        6    ______________________________________

EXAMPLE XIII

A test was performed to compare the effectiveness of brass comprisingabout 50 weight percent copper and brass comprising about 50 weightpercent zinc with brass comprising about 85 weight percent copper andabout 15 weight percent zinc. The brass in each instance was containedin a cylinder 10 centimeters high and 17/8 inches in diameter. The water(200 ml) containing 2.09 parts per million of lead added as lead nitratewas passed through the brass. The effluent lead in each instanceanalyzed less than 0.01 parts per million.

EXAMPLE XIV

Aluminum, arsenic, cadmium, lead and mercury were added to drinkingwater. The water was passed through brass containing about 50 weightpercent copper and about 50 weight percent zinc at a flow rate ofapproximately 0.50 gallons per minute with the following results.

    ______________________________________                CONCENTRATION                (PARTS PER MILLION)    METAL         INFLUENT   EFFLUENT    ______________________________________    Aluminum      0.46       <0.20    Arsenic       0.46       0.071    Cadmium       0.098      0.011    Lead          0.47       <0.05    Mercury       0.013      0.000    ______________________________________

EXAMPLE XV

Drinking water was passed through brass filings comprising about 50weight percent copper and 50 weight percent zinc. The input and outputwaters were analyzed for chemical content with the following results:

    ______________________________________                 CONCENTRATIONS                 (mg/l)    CHEMICAL       INPUT    OUTPUT    ______________________________________    Iron           0.260    0.017    Manganese      0.036    0.001    Copper         0.175    0.001    Fluoride       0.5      0.0    Magnesium      180.0    101.0    Zinc           0.101    0.001    Calcium        76.0     45.0    ______________________________________

EXAMPLE XVI

Brass filings (57 pounds) containing about 50 weight percent copper and50 weight percent zinc were placed into a 5 gallon container open at itstop and having a spout for the amount of liquid near its bottom. Water(5 gallons) having a hardness of 23 grains was poured into the containerthrough its top opening. The water passed through the brass filings andwas removed from the container through the spout. The water removed fromthe container was analyzed for its pH and hardness. Then the water waspoured back into the container and through the brass filings and thiswater on being removed from the container through the spout was alsoanalyzed for pH and hardness. This treatment was repeated for a total of4 cycles with the following results.

    ______________________________________    TIME                   HARDNESS    (MINUTES)       PH     (GRAINS)    ______________________________________    CYCLE 1     0              7      23    10              7.2    22    15              7.3    21    25              7.5    20    35              7.5    19.5    60              8.0    18    CYCLE 2    10              8.0    18    20              8.1    17    30              8.5    16    40              8.5    15    50              8.6    15    60              9.0    14    CYCLE 3    10              6.0    14    20              6.2    13    30              6.3    12    40              7.0    10    50              7.5    8    60              7.8    7     *pH adjusted to 6.0

    CYCLE 4    10              8.1    7    20              8.5    6    30              8.7    5    40              9.0    4    50              9.5    3    60              10.0   2    ______________________________________

The lowering in the hardness of water passed through brass containingabout 50 weight percent zinc and about 50 weight percent zincdemonstrates the effectiveness of the process of the present invention.

In addition to chemically treating undesirable constituents the methodof the present invention also has application to physically filteringundesirable suspended solids. This aspect of the present invention hasparticular application to removing suspended iron from water which ironis present in the water naturally, as a result of pretreatment such asby chlorination, or as a result of reaction with the bed of metallicparticles utilized in the present method. Where the water is pretreatedwith chlorine to treat dissolved iron, the present method will not onlyfilter the resulting suspended iron but also will treat the remainingchlorine in the water. The cannister housing the bed of metalparticulate matter can be periodically backwashed to remove any filteredmatter which has collected in the bed and to declog the bed. However,unlike in other treatment methods such as reverse osmosis andion-exchange methods, such backwashing does not result in the dumping ofconcentrated undesirable constituents.

Another alternative embodiment of the present invention is a method forpurification whereby the water is passed through both a bed of metallicparticulate matter such as brass and a bed of filter material and/orfilter aid such as sand to enhance filtration of undesirable suspendedmatter.

It will be appreciated by those skilled in the art that manymodifications and variations may be made without departing from thespirit and scope of the present invention. Accordingly the presentinvention is to be limited in scope only by the appended claims.

I claim:
 1. A method for reducing the concentration of a metal inliquids, said method comprising contacting a liquid containing at leastone metal selected from the group consisting of aluminum, arsenic,barium, cadmium, chromium, copper, iron, lead, selenium, manganese, goldand silver with a finely divided metal comprising an alloy of copper andzinc, and wherein the ratio by weight of said copper to said zinc isbetween about 1:9 and about 9:1.
 2. The method of claim 1 wherein theratio of said copper to said zinc in said alloy is between about 3:7 andabout 9:1.
 3. The method of claim 1 wherein said alloy is a brass alloy.4. The method of claim 1 wherein a metal contained in the liquid isaluminum.
 5. The method of claim 1 wherein a metal contained the liquidis arsenic.
 6. The method of claim 1 wherein a metal contained theliquid is iron.
 7. The method of claim 1 wherein a metal contained inthe liquid is lead.
 8. The method of claim 1 wherein a metal containedin the liquid is barium.
 9. The method of claim 1 wherein a metalcontained in the liquid is cadmium.
 10. The method of claim 1 wherein ametal contained in the liquid is chromium.
 11. The method of claim 1wherein a metal contained in the liquid is selenium.
 12. The method ofclaim 1 wherein the liquid is water.
 13. The method of claim 12 whereinthe water is drinking water.
 14. The method of claim 1 wherein theliquid is also contacted with activated carbon.
 15. The method of claim1 wherein a metal contained in the liquid is silver.
 16. The method ofclaim 1 wherein a metal contained in the liquid is copper.
 17. Themethod of claim 1 wherein a metal contained in the liquid is manganese.18. The method of claim 1 wherein a metal contained in the liquid isgold.
 19. The method of claim 1 wherein the liquid is passed through abed of said finely divided metal.
 20. The method of claim 1, whereinsaid finely divided metal is particles.